GB2117495A

GB2117495A - High speed vacuum gate valve

Info

Publication number: GB2117495A
Application number: GB08304434A
Authority: GB
Inventors: Richard John Hertel
Original assignee: Varian Associates Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1982-03-29
Filing date: 1983-02-17
Publication date: 1983-10-12
Also published as: DE3310592A1; NL8300642A; GB8304434D0; FR2524102A1; JPS58178066A

Abstract

A high speed, high vacuum gate valve employs tracks 21, 22 for guiding a closure member 14 between an open position and a closed position. The tracks each include a proximate portion adjacent the valve opening and extending rearwardly away from the opening, a distal portion extending laterally away from the opening and a curved portion connecting the proximate and the distal portions. The track is typically in the form of a groove in a track member and provides movement of the closure member free of abrupt changes in direction or speed. The valve is capable of operation in less than one second. The closure member is carried by links 28, 29 on a reciprocating carriage 26. <IMAGE>

Description

SPECIFICATION High speed vacuum gate valve Background of the invention This invention relates to vacuum gate valves and, more particularly, to high speed, high vacuum gate valves having a long operating life.

Vacuum gate valves are used in a variety of applications, one of which is in high energy particle accelerators. In certain of these applications, high speed and high reliability are of utmost importance.

For example, in ion implantation systems commercially used in the semiconductor industry, the path of the ion beam between the ion source and the target semiconductor wafer is maintained at a vacuum on the order of 10-7 torr. During changing of wafers, the wafer end of the system is sealed by a vacuum gate valve in order to minimize the volume which is repeatedly vacuum pumped. To maximize the throughput of the system, the wafer changing process, including operation of the vacuum gate valve, must take place in as short a time as possible.

Gate valve operation time must be on the order of 0.2 to 0.5 second. Furthermore, the gate valve must be highly reliable since system downtime to repair or replace the valve is undesirable. It will be obvious that high speed and high reliability are required in many commercial applications ofvacuum gate valves.

Prior art vacuum gate valves, while providing generally satisfactory operation, are not suited for high speed, long life operation. One type of gate valve, described by R.A. Childs in "Reliable UHV Gate Valves," Ind. Res./Dev., July 1978, includes a carriage pivotally coupled to a seal plate. The carriage and the seal plate travel linearly along a track until the seal plate strikes a mechanical stop.

The carriage continues to move along the track and causes the seal plate to pivot upward and seal the port. A gate valve utilizing a mechanical stop and a bar cam to press a seal plate against a vacuum port is disclosed in U.S. Patent No. 3,554,486. However, in valves employing a mechanical stop, the shock loads occurring when the seal plate strikes the stop at high speed cause rapid wear of the valve components. A high vacuum gate valve wherein the seal plate is mounted on a swinging arm and pivots laterally away from the port is disclosed in U.S. Patent No.

3,973,753 issued Aug. 10, 1976 to Wheeler. The disclosed valve is not suited for high speed operation.

It is a general object of the present invention to provide a new and improved high speed vacuum gate valves.

It is another object of the present invention to provide high speed vacuum gate valves having long life and high reliability.

It is yet another object of the present invention to provide high speed vacuum gate valves having a motion free of abrupt changes in direction or speed between an open position and a sealed position.

It is still another object of the present invention to provide high speed vacuum gate valves wherein high shock loading of the component parts during operation is avoided.

Summary ofthe invention According to the present invention, these and other objects and advantages are achieved in a high speed vacuum gate valve comprising a housing having an opening therein, a closure member for sealing the opening, track means adapted for guid ing the closure member between a sealed position and an open position and actuating means. The track means includes a proximate portion adjacent the opening and extending rearwardly away from the opening, a distal portion extending laterally away from the opening and a curved portion connecting the proximate and the distal portions. The track means guides the closure member so as to provide movement free of abrupt changes in direction or speed.The actuating means exerts a force on the closure member so as to move the closure member along a path defined by the track means between the open position and the sealed position.

Brief description of the drawings For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference may be had to the accompanying drawings which are incorporated herein by reference and in which: Figure 1 is a cross-sectional view of a vacuum gate valve in accordance with the present invention shown in the sealed position; Figure 2 is a cross-sectional view of the vacuum gate valve of Figure 1 taken along the line 2-2 thereof; Figure 3 is a cross-sectional view of the vacuum gate valve of Figure 1 taken along the line 3-3 thereof; Figure 4 is a cross-sectional view of the vacuum gate valve of Figure 1 shown in the open position; Figure 5 is a cross-sectional view, taken along the line 5-5 of Figure 4, of the vacuum gate valve in the open position;; Figure 6 is a cross-sectional view of another preferred embodiment of a vacuum gate valve in accordance with the present invention; Figure 7 is a cross-sectional view of the vacuum gate valve of Figure 6 taken along the line 7-7 thereof; and Figure 8 is a cross-sectional view of the vacuum gate valve of Figure 6 taken along the line 8-8 thereof.

Detailed description of the invention A preferred embodiment of a high speed vacuum gate valve in accordance with the present invention is shown in Figures 1-5. The valve includes a housing 10 having an opening 12therein and a closure member 14 for sealing the opening 12. The valve further includes track means for guiding the closure member 14 between a sealed position as shown in Figures 1-3 and an open position as shown in Figures 4 and 5. In the embodiment of Figures 1-5, the track means includes a track member 16 having tracks 17, 18 and a track member 20 having tracks 21, 22. The valve also includes an actuating means for exerting a force on the closure member 14 so as to move the closure member 14 along a path defined by the tracks 17, 18,21,22 between the open position and the sealed position.In the embodiment of Figures 1-5, the actuating means includes a carriage 26 coupled to the closure member 14 by linkage bars 28,29. The linkage bars 28 and 29 are parallel and have equal lengths. The carriage 26 is guided along a linear path by tracks 30,31 in the track members 20, 16, respectively, and is adapted for coupling to an actuating source, which, in the embodiment of Figures 1-5, is an air actuated piston 34 coupled to the carriage 26 by a connecting rod 36.

A linear seal 38 provides a seal around the connecting rod 36 where it passes through the housing 10.

The linear seal 38 employ known techniques for sealing a linearly movable rod. A small volume around the rod 36 and between two O-rings i vacuum pumped to insure a high vacuum seal.

The housing 10 can be a housing for a selfcontained gate valve, in which case the housing has a second opening typically aligned with the first opening 12. Alternatively, the housing 10 can be the housing for equipment which operates under vacuum, such as an ion implanter. The opening 12 is typically circular and is several inches in diameter.

The closure member 14 includes a seal plate 40 with an O-ring 42 positioned in an O-ring groove around the periphery of the front surface of the seal plate 40. A trunnion 44 is positioned in the center of the rear surface of the seal plate 40 and is coupled rigidly thereto. The linkage bar 28 is pivotally attached to the trunnion 44 by a pin 46. A trunnion 45, positioned in the lower portion of the rear surface of the seal plate 40, is pivotally attached to the linkage bar 29 by a pin 47. Roller supports 50, 52 extend rearwardly from the rear surface of the seal plate 40. The roller supports 50 and 52 are spaced above and below the center of the seal plate 40 by equal distances and are positioned adjacent to the tracks 17, 18,21,22. Rollers 54 are attached to the roller supports 50, 52 so as to engage the tracks 17, 18,21,22 as described hereinafter.

The tracks 17, 18,21,22 are in the form of elongated grooves. The grooves can be formed in opposite parallel walls of the housing 10 or can be formed in parallel track members 16,20 rigidly attached to the housing 10 on opposite sides of the opening 12. The tracks 21,22 will now be described in detail with reference to Figures 3. It will be realized that the tracks 17, 18 are mirror images of the tracks 21,22. The tracks 21,22 include proximate portions 21 a, 22a adjacent the opening 12 and extending rearwardly away from the opening 12. The tracks 21, 22 further include distal portions 21 b, 22b extending laterally away from the opening 12.In the embodiment of Figures 1-5, the distal portions 21 b, 22b are parallel to the plane of the opening 12, and the proximate portions 21 a, 22a are perpendicular to the plane of the opening 12. The proximate portions 21a, 22a are connected by curved portions 21 a, 22c to the distal portions 21 b, 22b respectively. The proximate portions 21a, 22a, the distal portions 21b, 22b and the curved portions 21c, 22c combine to form continuous, uninterrupted paths free of abrupt changes in direction or speed between the sealed position and the open position. The proximate portions 21 a, 22a are spaced relative to the opening 12 so as to engage the rollers 54 and to center the seal plate 40 on the opening 12.

The carriage 26 includes a carriage body 66 with rollers 68 attached thereto on opposite sides. The tracks 30,31 can be elongated grooves in the track members 20, 16, respectively. The rollers 68 are positioned so as to engage the tracks 30,31. The carriage 26 further includes trunnions 70,71 rigidly coupled to the body 66. The trunnion 70 is pivotally coupled to the linkage bar 28 by a pin 72. The trunnion 71 is pivotally coupled to the linkage bar 29 buy a pin 73.

In operation, the closure member 14 moves between the sealed position shown in Figures 1-3 and the open position shown in Figures 4 and 5 along a path defined by the tracks 17,18,21,22. The closure member 14 is actuated by the carriage 26, which moves along a path defined by the tracks 30, and which exerts a force on the closure member 14 through the linkage bar 28. The linkage bar 29 operates to stabilize the closure member 14 in a plane parallel to the opening 12 during movement between the open position and the sealed position and is not a load bearing member. While the linkage bar 29 is not a required element of the vacuum gate valve, it provides more stable operation, particularly at lower speeds. The carriage 26 is operated by the air actuated piston 34.Starting in the open position, the connecting rod 36 pushes the carriage 26 and the closure member 14 downward. The carriage 26 moves continuously along the tracks 30,31. The rollers 54 attached to the closure member 14 roll along the distal portions 21 b, 22b of the tracks 21, 22 and the corresponding distal portions of the tracks 17, 18. During this portion of the movement, the closure member 14 and the carriage 26 remain in a fixed relationship to each other. When the rollers 54 reach the curved portions 21 c, 22c of the tracks 21, 22, the rollers 54 and the entire closure member 14 follow the path defined by the tracks 17, 18,21,22 and change direction toward the opening 12. Due to the curvature of the portions 21 c, 22c, the change of direction is gradual and continuous and the closure member 14 is not subjected to shock loading.As the closure member 14 moves away from the carriage 26 and toward the opening 12, the linkage bar 28 pivots about the pins 46 and 72 and the linkage bar 29 pivots about the pins 47 and 73. When the rollers 54 reach the proximate portions 21a, 22a of the tracks 21, 22, the movement of the closure member 14 is perpendicular to the plane of the opening 12.

Thus, as the closure member 14 makes contact with the periphery of the opening 12, there is no scuffing of the O-ring 42. Furthermore, as the closure member 14 moves toward the sealed position, the carriage 26 continues to move downward in a linear fashion, thereby increasing the force component applied to the closure member 14 in the direction perpendicular to the plane of the opening 12. This force component tends to compress the O-ring 42 and improve the quality of the seal. As the closure member 14 approaches the sealed position, it decel erates gradually due to the pivotal motion of the linkage bar 28,29, thus avoiding slamming of the closure member 14 into the sealed position. The carriage 26 is moved past top dead center relative to the closure member 14 by a short distance so as to lock the closure member 14 in the sealed position.

When the closure member 14 is moved from the sealed position to the open position, the abovedescribed sequence is reversed and the tracks 17,18, 21,22 guide the closure member 14to the open position.

Another embodiment of a high speed vacuum gate valve in accordance with the present invention is shown in Figures 6-8. The valve includes a housing 110 having an opening 112 therein and a closure member 1 l4forsealing the opening 112. In the embodiment of Figures 6-8, the track means includes a track member 120 having a track 122 on one side of the closure member 114 and a track member 116 on the opposite side of the closure member 114 having a track 118 parallel to and a mirror image of the track 122. The actuating means includes a carriage 126 coupled to the closure member 114 by linkage bars 128, 129. The carriage 126 is guided along a linear path by a track 130 in the track member 120 and a track 131 in the track member 116 and is adapted for coupling to an actuating source by a connecting rod 136.The embodiment of Figures 6-8 utilizes a single pair of tracks for guiding the closure member 114 whereas the embodiment of Figures 1-5 utilizes two pairs of tracks for guiding the closure member 14.

The closure member 114 includes a seal plate 140 with an O-ring 142 positioned in an O-ring groove in the front surface of the seal plate 140. Atrunnion 144, positioned in the center of the rear surface of the seal plate 140, is pivotally attached to the linkage bar 128 by a pin 146. A trunnion 145, positioned in the lower portion of the rear surface of the seal plate 140, is pivotally attached to the linkage bar 129 by a pin 147. Roller supports 150, positioned on opposite sides of the trunnion 144 adjacent to the tracks 118, 122, are attached to the rear surface of the seal plate 140. Rollers 154 are attached to the roller supports 150 so as to engage the tracks 118, 122.

The tracks 118, 122 are similar to the tracks 17, 18, 21,22 shown and described hereinabove. The tracks 118, 122 are in the form of elongated grooves in the track members 116, 120. The track member 122 includes a proximate portion 122a adjacent the opening 112 and extending rearwardly away from the opening 112. Since there is only one track per side, the proximate portion 122a of the track 122 is located adjacent to the center of the closure member 140.The track 122 further includes a distal portion 122b extending laterally away from the opening 112 and a curved portion 122c connecting the proximate portion 122a and the distal portion 122The portions 122a, 122b, 122e combine to form a continuous, uninterrupted path free of abrupt changes in direction or speed between the sealed position and the open position.

The carriage 126 includes a carriage body 166 with rollers 168 attached thereto on opposite sides. The tracks 130, 131 can be grooves in the respective track members 120, 116. The rollers 168 are positioned so as to engage the tracks 130, 131.Thecarriage 126 further includes a trunnion 170 pivotally coupled to the linkage bar 128 by a pin 172 and a trunnion 171 pivotally coupled to the linkage bar 129 by a pin 173.

The linkage bars 128 and 129 are parallel and have equal lengths. Thus, as the closure member moves between the sealed position and the open position it remains parallel to the plane of the opening 112.

In operation, the closure member 114 moves between the sealed position as shown in Figures 6-8 and the open position along a path defined by the tracks 118, 122. The closure member 114 is actuated by the carriage 126 which moves along a path defined by the tracks 130, 131 and which exterts a force on the closure member 114 through the linkage bar 128. The movement of the closure member 114 and the carriage 126 between the sealed position and the open position is the same as that described hereinabove in connection with the vacuum gate valve shown in Figures 1-5. There is no shock loading of the components of the gate valve, and there is no scuffing of the O-ring. The linkage bar 129 is utilized to stabilize the closure member 114 in a plane parallel to the plane of the opening 112 and is not a load-bearing member.

The tracks which guide the closure members in both of the embodiments described hereinabove have curved portions which connect proximate portions and distal portions. The curved portion of the track provides a transition free of abrupt changes in direction or speed between rearward movement away from the opening and lateral movement away from the opening. While any continuous curve is suitable, an arc portion of a circle is preferred for high speed operation. The radius of curvature is an important factor in limiting the acceleration or deceleration force applied to the assembly during high speed operation. Asmall radius of curvature results in a greater strain on the assembly as it passes through the curved portion.While the tracks have been shown as elongated grooves, it will be obvious to those skilled in the art that other types of tracks can be used without departing from the scope of the present invention. Also, it is not necessary that the distal portion of the tracks, the portion which guides the closure member laterally away from the opening, be parallel to the opening. It is simply necessary that the distal portion of the track guide the closure member laterally away from the opening so that the closure member does not block the opening in the open position. The proximate portion of the track is preferably perpendicular, or nearly perpendicular, to the plane of the opening so as to avoid scuffing and wear of the O-ring as the closure member comes into contact with the periphery of the opening.

In one example of a high speed vacuum gate valve in accordance with the embodiment of Figures 1-5, the opening 12 was about 8 inches, the radius R of the curved portions 21c, 22c was 0.56 inch and the speed of operation was 0.5 second. With the radius R of 0.56 inch, the acceleration of the mechanism is limited to approximately one "g". This valve was successfully tested for over one miilion operations, requiring only the replacement of the linear seal O-rings after each 500,000 operations.

Thus, there is provided by the present invention a high speed vacuum gate valve in which shock loading of the mechanism is avoided and in which frictional wear of the O-ring is avoided. The configuration permits high speed operation of the valve; that is, operation in under one second. Furthermore, the configuration results in highly reliable, long-life operation.

While there has been shown and described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

1. A high speed vacuum gate valve comprising: a housing having an opening therein; a closure member for sealing said opening; track means adapted for guiding said closure member between a sealed position and an open position, said track means including a proximate portion adjacent said opening and extending rearwardly away from said opening, a distal portion extending laterally away from said opening and a curved portion connecting said proximate and said distal portions, said track means guiding said closure member so as to provide movement free of abrupt changes in direction or speed; and actuating means for exerting a force on said closure member so as to move said closure member along a path defined by said track means between said open position and said sealed position.

2. The vacuum gate valve as defined in claim 1 wherein said proximate portion of said track means is generally perpendicular to the plane of said opening.

3. The vacuum gate valve as defined in claim 1 wherein said curved portion of said track means has the general shape of an arc portion of a circle.

4. The vacuum gate valve as defined in claim 1 wherein said distal portion of said track means is generally parallel to the plane of said opening.

5. The vacuum gate valve as defined in claim 2 wherein said actuating means includes a carriage adapted for movement parallel to said distal portion and linkage means for pivotally coupling said carriage to said closure member.

6. The vacuum gate valve as defined in claim 5 wherein said linkage means includes a pair of parallel, spaced apart linkage members, each pivotally coupled to said closure member and pivotally coupled to said carriage, wherein said closure member remains parallel to the plane of said opening during movement between said sealed position and said open position.

7. The vacuum gate valve as defined in claim 6 wherein said carriage, during actuation of said closure member to said sealed position, moves past a point corresponding to said sealed position so as to lock said closure member in said sealed position.

8. The vacuum gate valve as defined in claim 1 wherein said track means including a track member and wherein said proximate, said distal and said curved portions of said track means are in the form of an elongated groove in said track member.

9. A high speed vacuum gate valve comprising: a housing having an opening therein; a closure member for sealing said opening: a pair of track members positioned on opposite sides of said closure member and adapted for guiding said closure member between a sealed position and an open position, each track member including a track, each track including a proximate portion adjacent said opening and extending rearwardly away from said opening, a distal portion extending laterally away from said opening and a curved portion connecting said proximate and said distal portions, said tracks guiding said closure member so as to provide movement free of abrupt changes in direction or speed; and actuating means for exerting a force on said closure member so as to move said closure member along a path defined by said tracks between said open position and said sealed position.

10. The vacuum gate valve as defined in claim 9 wherein each of said tracks is in the form of an elongated groove in said track member.

11. The vacuum gate valve as defined in claim 9 wherein said proximate portion of each track is generally perpendicular to the plane of said opening.

12. The vacuum gate valve as defined in claim 10 wherein said closure member includes rollers mounted for engagement with said grooves so as to provide rolling movement of said closure member along said grooves.

13. The vacuum gate valve as defined in claim 12 wherein said actuating means includes a carriage adapted for movement parallel to said distal portion and a linkage member for pivotally coupling said carriage to said closure member.

14. The vacuum gate valve as defined in claim 9 wherein said curved portion of each track has the general shape of an arc portion of a circle.

15. The vacuum gate valve as defined in claim 14 wherein said distal portion of each track is generally parallel to the plane of said opening.

16. The vacuum gate valve as defined in claim 15 wherein said track members are coupled to opposite walls of said housing.

17. The vacuum gate valve as defined in claim 16 wherein each track member further includes a carriage track for guiding said carriage.

18. The vacuum gate valve as defined in claim 17 wherein said carriage, during actuation of said closure member to said sealed position, moves past a point on said carriage track corresponding to said sealed position so as to lock said closure member in said sealed position.

19. A high speed vacuum gate valve comprising: a housing having an opening therein; a closure member for sealing said opening; said housing including a pair of wall members positioned on opposite sides of said closure member and adapted for guiding said closure member between a sealed position and an open position, each wall member including a track comprising a proximate portion adjacent said opening and extending rearwardly away from said opening, a distal portion extending laterally away from said opening and a curved portion connecting said proximate and said distal portions, said tracks guiding said closure member so as to provide movement free of abrupt changes in direction or speed; and actuating means for exerting a force on said closure member so as to move said closure member along a path defined by said tracks between said open position and said sealed position.

20. The vacuum gate valve as defined in claim 19 wherein said proximate portion of each track is generally perpendicular to the plane of said opening.

21. The vacuum gate valve as defined in claim 20 wherein said curved portion of each track has the general shape of an arc portion of a circle.

22. The vacuum gate valve as defined in claim 21 wherein each of said tracks is in the form of an elongated groove in said wall members and said closure member includes rollers mounted for en gagementwith said grooves so as to provide rolling movement of said closure member along said grooves.